1. Field of the Invention
The present invention relates to an apparatus for measuring a specific molecule contained in body fluid and in particular to an optical waveguide type iontophoresis sensor chip and a method for packaging a sensor chip.
2. Description of the Related Art
A planar lightwave circuit sensor using optical waveguide phenomenon is widely spread as the sensor to measure the amount of the bio molecules existing in body fluid such as blood. The planar lightwave circuit sensor has a light source, a substrate receiving a light from the light source, and a pair of diffraction gratings disposed on the substrate. Between the pair of diffraction gratings, a single optical waveguide membrane is disposed on the substrate so as to transmit the incident light. Further, an analyzing membrane is disposed on the optical waveguide membrane. The analyzing membrane identifies the bio molecules and transforms the information about the amount of the identified bio molecules to a change of an optical intensity.
An existing method for analyzing the bio molecules contained in the blood by the planar lightwave circuit sensor is as follows. At first, the blood is collected from vein with a syringe. The collected blood is dropped on the analyzing membrane. The laser light is emitted and diffracted by a diffracting grating. The diffracted light penetrates the optical waveguide membrane. The evanescent wave is generated at the interface between the optical waveguide membrane and the analyzing membrane. The intensity of the evanescent wave changes by reaction between the dropped bio molecules contained in the blood and reagent contained in the analyzing membrane. By detecting the changes of the evanescent wave intensity, the bio molecules contained in the blood is analyzed as disclosed in Japanese Patent Application Hei9-61346.
On the other hand, a reverse iontophoresis method has also been studied recently. By the reverse iontophoresis method, the specific molecule is extracted from the living body through the skin with an electric current. Also, applying the reverse iontophoresis method to extract glucose from the living body without injury is attempted. By decomposing the extracted glucose with enzyme and detecting the amount of electron during the chemical reaction as the change of electric current, the enzyme electrode method is applied to develop an apparatus for measuring the glucose as disclosed in published Japanese Patent Application 2000-227 and published Japanese Patent Application 2002-191582.
However, the planar lightwave circuit sensor requires pricking part of the body with a needle and squeezing the body part. Though the enzyme electrode method does not require pricking the body, the result may be affected by the amount of enzyme contained in the extracted body fluid. Also, existing the enzyme electrode method using an electrode and immobilized glucose oxidase (GOD) can't continue the measurement after enzyme is exhausted.